1. Field of the Invention
The present invention relates to universal optical fiber connectors and their basic plugs, wherein the optical fiber connectors have some common elements for their connector-functions to permit an installation of optical fiber into one of the different type connectors for establishing their connector to connector connection more easily and to facilitate a tuning operation with positioning key maintaining the same direction between eccentricity of the fiber core and the key.
For the sake of clarity, in general, the technical term "optical fiber connectors" means all of the elements where each of them is terminated on an end portion of an optical fiber. Conceptually, the optical fiber connector may be of any shape, such as a plug with a tip formed as a male member, an adapter with a tip formed as a female member, a combination thereof, or the like.
2. Description of Related Art
Heretofore, an optical fiber connector has the configuration in which a ferrule is coupled to a plug flame after fixing an optical fiber into the center of the ferrule to establish a connection between different optical fibers in opposite directions.
A FC-type plug as an example of such conventional optical fiber connector is depicted in FIG. 24. As shown in the figure, the FC-type plug comprises a ferrule 101, a frame 102, and a tightening member 103, with an integrated configuration of coaxially arranging these elements around a bare optical fiber 99 as the center thereof. Furthermore, there is a key ring 104 oriented along a direction of a displacement of the center of the bare optical fiber 99 fixed in the ferrule 101.
For coupling the plugs 100 together, it is necessary to provide an adapter 201 for connecting plugs to its ends, respectively. The adapter 201 is comprised of a flange portion 202 and a cylindrical portion 203 in a one-piece design. An outer peripheral surface of the cylindrical portion 203 has a male screw thread 204 and a depressed portion 205. Also, a mating slot 206 is concentrically formed in the center of the cylindrical portion 203. In an inner side of the mating slot 206, there is a separate sleeve 207 on which the ferrule 101 of the plug 100 is fit and attached in a removable manner.
For coupling the plug 100 with the adapter 201, a positioning key 104a is engaged into the depressed portion 205 in addition to fitting the ferrule 101 of the plug 100 into the separate sleeve 207 of the adapter 201 to adjust their positions so as to be in their right places in a circumferential direction. Then a female thread 105a of a coupling nut 105 is screwed to a male screw thread 204, so that the plug 100 is coupled to the adapter 201 tightly and thus it prevents them from becoming detached.
Up to the present, optical fiber connectors of the FC, SC, ST type, and so on with various connection forms have been commercially used. In this case, the different type optical fiber connectors are grouped together so as to put them to proper use. Under certain circumstances such as the changing of a system configuration, the need for the mutual connection between the different types of optical fiber connectors comes about and thus a converting adopter is required. Therefore, there are several problems including that many different types of converting adapters should be prepared so as to be used in the mutual connection and a quality of signal to be transmitted is decreased as an optical loss in optical transmission path is increased.
Conventionally, furthermore, it is very difficult to detach the key ring when it should be shifted in the right place to adjust eccentricity of the fiber core after the completion of the connector assembly. Depending on the connector type, moreover, the position of the key ring cannot be re-adjusted.
There may be cases where the optical fiber connector is fitted to an end portion of an optical fiber cable or an optical fiber code in installing the necessary wiring in a building, a mechanical system, or the like. In this case, optical fiber connectors of the FC, SC, ST type, and so on with various connection forms should be selected and combined to proper use depending on their applications.
Under certain circumstances, such as the changing of a system configuration, the need for the mutual connection between the different types of optical fiber connectors comes about and thus a converting adapter is required. Therefore, there are several problems including that many different types of converting adapters should be prepared so a to be used in the mutual connection and a quality of signal to be transmitted is decreased as an optical loss in optical transmission path is increased.
In general, an adapter to be provided as a coupling portion of the optical fiber connector has two end portions, one for fixing on a fixing member such as a panel and the other for receiving a plug to be fixed to an optical fiber cable or the like.
There may be cases where a ferrule's tip of the plug fixed through the adapter requires cleaning for preventing a loss in the optical transmission path. However, there is a problem that it is very difficult to clean the ferrule's tip of the plug in a state of being coupled with the adapter.
To solve those problems laid-open, Japanese Patent Application No. 122570/1996 discloses a tightening mechanism of a plug that allows removal of an adapter from its fixing member.
According to the above document, there is a problem that the method is costly performed because it requires an intricate structure for laterally fixing a standard type plug on a fixing member such as a panel in a special shape.
For using the optical fiber connector in installing the necessary wiring in a building or a mechanical system, as described above, the optical fiber connector should have an excellent strength against bending stress.
For various use in various environments, the optical fiber connector should have long term stability.